Your graph should look exactly like the one below.
y = x + 2 (Black)
x + y = 3 (Red)
Now the solution is found in the intersection of the points, which is (0.5,2.5)
Verify:
y = x + 2
2.5 = 0.5 + 2
2.5 = 2.5 (correct)
Cheers
